However, scientists say it is hormonal, in that it’s related to a hormone released by the placenta, and claim it gives us an evolutionary advantage by protecting the baby from toxins.

Supporting this theory is the fact that women who have no morning sickness are more likely to miscarry.

Scientists reckon animal products, including meat and fish, are more likely to harm a mother-to-be’s immune system (which is already suppressed during pregnancy), which explains why eating these more bacteria-heavy foods can induce vomiting.

The more severe strain of morning sickness is called Hyperemesis gravidarum and it occurs in about 1.6 per cent of all cases, and the likes of the Duchess of Cambridge have suffered with it.

There are treatments available for morning sickness and taking prenatal vitamins before pregnancy can reduce the risk of symptoms.